Combine a Mat map and a Normal map in Blender?
The answer is yes you can do that. I am assuming you are working in the Blender Render Environment and not cycles as their material workflow is quite different.
Attached is the file for your reference. The material is an old 3dsmax metallic material and the normals map has been generated using shadermap3.



For Blender Render workflow.
1. Create a new material on the material Tab on the properties panel.
2. Next go to the texture Tab on the properties panel.  

Settingup Albedo/Diffuse Map
3. Select an empty texture slot and click on "New"
4. Select open and point to your Albedo map on your harddrive.
5. Under Influence Header make sure "Color" is checked.  

Setting up Normals Map
6. Select another empty texture slot and click on "New" again.
7. Select open and point to your Normals map on your harddrive.
8. Under Image Sampling Header make sure "Normal map" Option is checked.
9. Under Influence Header make sure only "Normal" is checked.

Here on out you should be able to see the normals texture in the viewport in "Textured Mode". Remember to add some light source or else your scene will just be blackish and dark.





Happy Blending!